2004 FX4 5.4L
Stock Borg Warner 4406
Transmission shifts fine and noise only occurs in 4x4.

Was driving in the snow the other day and decided to use the 4x4. I noticed that under moderate acceleration I get a loud metallic "thud" noise coming from the T-case area and feels like the bottom of the truck is going to fall off. Its very noticable.

With the window down I tried to get a better listen to the noise. It made the "thud" noise again followed by a short "Buzzing" sound. It was hard to tell where exactly the buzzing was coming from.

From a stop sign if I get into the throttle about half-way, I noticed that the problem can be recreated when the front tires lose traction.

I'm getting ready to take apart both front hubs this weekend just incase it may be an IWE engagement issue. I do some light off roading and occasionaly mud is involved so its possible they may need to be cleaned up.

If the T-case needs to be rebuilt im prepared to tear it down if I cant find a good donor.

Any suggestions appreciated.

 

sounds more like an IWE problem...

 

Thanks techrep

was too cold here over the past weekend to investigate. I will post results when I have them in case anyone else has this problem.

 

roger that

 

While you're at it, inspect the u-joints.

 

Update:

It was an IWE engagement issue. Drivers side would only engage halfway and when it slips it spins faster than the other side.. the loud bang was it engaging while spining faster. Luckily it didnt destroy my CV axle.

Solution:

Rather than buying new parts I went ahead and cleaned out the entire assembly. There was alot of corrosion and dirt and mud packed in there not allowing full engagement. After flushing everything out with parts cleaner I pulled the dust cap off the bearings inside the hub assembly and repacked them with some synthetic bearing grease. Put it all back together tonight and test drove it.

4WD engages and disengages fine now with no unusual noises.

Hope this thread helps someone out in the future.